Sudoku Instructions

Rules for solving sudoku puzzles are simple.
Complete each blank square in a puzzle with the correct number.
There are three very simple constraints to follow.
In a 9x9 sudoku puzzle using numbers, the following must contain all digits 1-9 in any order. Each:

9-block row

9-block column

3x3 subsection

The same constraints can be applied to puzzles of different sizes.
For example, 4x4 puzzles must have the numerals 1-4 in each row, column and 2x2 subsection.
Larger 16x16 sudoku puzzles must have numerals 1-16 in each row, column and subsection.
The principles are the same whatever the size of the game and also when letters are used.
With letters, each letter must be used but only one time in each row, column, and subsection.
4x4, 9x9, 16x16, 25x25.

Every sudoku puzzle begins with some blocks already filled in.
Puzzle difficulty is largely a function of how many squares are filled in.
The more squares that are known, the easier it is to figure out which numbers or letters go in the empty blocks.
As you fill in blocks correctly, options for the remaining blocks reduces and it becomes easier to fill them in.
This site offers the following difficulty levels:
Easy, Medium, Hard, MENSA, Genius, Lex Luthor.

Solutions can be generated online and printed if you need help or to check your progress.

Sudoku Strategy

Need help solving sudoku puzzles? Try these tips.
Begin by scanning for a weakness.
It will be obvious in easy sudoku puzzles with many blocks already completed.
Some may have entire rows or columns filled in which make it easy to figure out remaining empty blocks in a subsection.

History of Sudoku

Our Japanese friends tell us "sudoku" means something like "single number" referring to the solitary position of each number in the puzzle grid. Although the sound "doku" may also mean, "poison" which would be interesting; "poison number". Maybe it seems that way when a wrong number is selected. As in most languages, one sound can be associated with several meanings. And when translating into English, it has also been spelled either "su doku", "soduko", "sudoko", or "suduko". Sometimes puzzle is mispelled as "puzzel". Anyway, although sudoku puzzles were popularized in Japan, they're actually of European origin being similar to a mathematic concept called "Latin Squares". Each square is a table or grid in which a number or symbol appears only once in each row and column. In 1979, a puzzle maker (Howard Garnes) expanded the Latin Squares concept to create what was then called "Number Place". Then, Maki Kaji, President of a Japanese puzzle company, began publishing Number Place puzzles there but called them "Suji wa dokushin ni kagiru" which translates roughly as "the numbers must be single". Later he limited the number of clues, imposed rules about the symmetry of their appearance, and shortened the puzzle's name to just sudoku. Since these changes, soduko puzzles became increasingly popular in Japan. Later, with the help of Wayne Gould, sudoku's spread back to America and now globally. So, although the puzzles have European and American roots, many regard Maki Kaji as the Father of Sudoku.